1. Field of the invention
The present invention concerns a torque generator device for simulating a load opposing a force. The force in question can be either a physical force exerted by a user or a mechanical force exerted by a structure or apparatus to which a counterweight must be applied. This invention finds a specific application in the field of physical exercise apparatus such as muscle exercise or rehabilitation apparatus.
2. Description of the Prior Art
Such physical exercise apparatus usually includes a load opposed by the muscular force of a user acting on an exercise member mechanically coupled to said load. These exercise members can be means such as bars, handles, pedals or the like and are referred to hereinafter as "exercise bars". This type of apparatus usually includes a cast iron weight which has to be lifted in a first work phase and held back on returning to its rest position in a second work phase. The first or "concentric" work phase shortens the user's muscles and the second or "eccentric" work phase involves controled extension of the users' muscles. The structure of the mechanical coupling between the cast iron weight and the exercise bar determines how much the latter moves and consequently the type of physical exercise provided by the apparatus. Most muscle exercise and rehabilitation exercises can be carried out using apparatus of this kind.
Proposals have been made to substitute a torque generator for the cast iron weights, capable of simulating their effect. This type of torque generator apparatus includes a direct current electric motor and an associated control device producing a torque resisting the force applied by the user during "concentric" work and exerting a force which must be opposed by the user during "eccentric" work.
In practice load simulator apparatus of this kind suffers from numerous drawbacks due in particular to the use of a direct current motor. For example, direct current motors cannot produce maximal torque at low speed and so the load simulator apparatus must have considerable gearing down between the motor and the exercise bar. This limits the maximum speed at which the exercise bar can be moved and also increases the effect of the inertia of the motor when its direction of rotation is changed, for example on changing from a "concentric" work phase to an "eccentric" work phase. Also, direct current motors are costly, heavy and bulky and have substantial maintenance requirements.
The present invention is directed to a torque generator device for simulating a load opposing a force which can, among other things, overcome these drawbacks.